http://xml.apache.org/xalan-j/: Serializer to write out XML, HTML etc. as a stream of characters from an input DOM or from input SAX events. (The Apache Software Foundation) 
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 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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/*
 * $Id: XPathExpressionImpl.java 1225426 2011-12-29 04:13:08Z mrglavas $
 */


package org.apache.xpath.domapi;

import javax.xml.transform.TransformerException;

import org.apache.xpath.XPath;
import org.apache.xpath.XPathContext;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
import org.apache.xpath.res.XPATHMessages;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.xpath.XPathException;
import org.w3c.dom.xpath.XPathExpression;
import org.w3c.dom.xpath.XPathNamespace;


The class provides an implementation of XPathExpression according 
to the DOM L3 XPath Specification, Working Group Note 26 February 2004.

See also the Document Object Model (DOM) Level 3 XPath Specification.


The XPathExpression interface represents a parsed and resolved 
XPath expression.


See Also:
  • XPathExpression
@xsl.usageinternal
/**
 * 
 * The class provides an implementation of XPathExpression according 
 * to the DOM L3 XPath Specification, Working Group Note 26 February 2004.
 *
 * <p>See also the <a href='http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document Object Model (DOM) Level 3 XPath Specification</a>.</p>
 *
 * <p>The <code>XPathExpression</code> interface represents a parsed and resolved 
 * XPath expression.</p>
 * 
 * @see org.w3c.dom.xpath.XPathExpression
 *  
 * @xsl.usage internal
 */
class XPathExpressionImpl implements XPathExpression {

  
The xpath object that this expression wraps

/**
   * The xpath object that this expression wraps
   */
  final private XPath m_xpath;
  
  
The document to be searched to parallel the case where the XPathEvaluator
is obtained by casting a Document.

/**
   * The document to be searched to parallel the case where the XPathEvaluator
   * is obtained by casting a Document.
   */  
  final private Document m_doc;  

    
Constructor for XPathExpressionImpl.

Params:
  • xpath – The wrapped XPath object.
  • doc – The document to be searched, to parallel the case where''
           the XPathEvaluator is obtained by casting the document.
/**
     * Constructor for XPathExpressionImpl.
     * 
     * @param xpath The wrapped XPath object.
     * @param doc The document to be searched, to parallel the case where''
     *            the XPathEvaluator is obtained by casting the document.
     */
    XPathExpressionImpl(XPath xpath, Document doc) {
        m_xpath = xpath;
        m_doc = doc;
    }

    
This method provides an implementation XPathResult.evaluate according 
to the DOM L3 XPath Specification, Working Group Note 26 February 2004.

See also the Document Object Model (DOM) Level 3 XPath Specification.


Evaluates this XPath expression and returns a result.


Params:
  • contextNode – The context is context node for the 
  evaluation of this XPath expression.If the XPathEvaluator was 
  obtained by casting the Document then this must be 
  owned by the same document and must be a Document, 
  Element, Attribute, Text, 
  CDATASection, Comment, 
  ProcessingInstruction, or XPathNamespace 
  node.If the context node is a Text or a 
  CDATASection, then the context is interpreted as the 
  whole logical text node as seen by XPath, unless the node is empty 
  in which case it may not serve as the XPath context.
  • type – If a specific type is specified, then the 
  result will be coerced to return the specified type relying on 
  XPath conversions and fail if the desired coercion is not possible. 
  This must be one of the type codes of XPathResult.
 @param result The result specifies a specific result 
  object which may be reused and returned by this method. If this is 
  specified as nullor the implementation does not reuse 
  the specified result, a new result object will be constructed and 
  returned.For XPath 1.0 results, this object will be of type 
  XPathResult.
Throws:
  • XPathException – 
  TYPE_ERR: Raised if the result cannot be converted to return the 
  specified type.
  • DOMException – 
  WRONG_DOCUMENT_ERR: The Node is from a document that is not supported 
  by the XPathEvaluator that created this 
  XPathExpression.
  
    NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
  context node.
See Also:
  • XPathExpression.evaluate(Node, short, XPathResult)
Returns:The result of the evaluation of the XPath expression.For XPath 
  1.0 results, this object will be of type XPathResult.
@xsl.usageinternal
/**
     *
     * This method provides an implementation XPathResult.evaluate according 
     * to the DOM L3 XPath Specification, Working Group Note 26 February 2004.
     *
     * <p>See also the <a href='http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document Object Model (DOM) Level 3 XPath Specification</a>.</p>
     * 
     * <p>Evaluates this XPath expression and returns a result.</p>
     * @param contextNode The <code>context</code> is context node for the 
     *   evaluation of this XPath expression.If the XPathEvaluator was 
     *   obtained by casting the <code>Document</code> then this must be 
     *   owned by the same document and must be a <code>Document</code>, 
     *   <code>Element</code>, <code>Attribute</code>, <code>Text</code>, 
     *   <code>CDATASection</code>, <code>Comment</code>, 
     *   <code>ProcessingInstruction</code>, or <code>XPathNamespace</code> 
     *   node.If the context node is a <code>Text</code> or a 
     *   <code>CDATASection</code>, then the context is interpreted as the 
     *   whole logical text node as seen by XPath, unless the node is empty 
     *   in which case it may not serve as the XPath context.
     * @param type If a specific <code>type</code> is specified, then the 
     *   result will be coerced to return the specified type relying on 
     *   XPath conversions and fail if the desired coercion is not possible. 
     *   This must be one of the type codes of <code>XPathResult</code>.
    *  @param result The <code>result</code> specifies a specific result 
     *   object which may be reused and returned by this method. If this is 
     *   specified as <code>null</code>or the implementation does not reuse 
     *   the specified result, a new result object will be constructed and 
     *   returned.For XPath 1.0 results, this object will be of type 
     *   <code>XPathResult</code>.
     * @return The result of the evaluation of the XPath expression.For XPath 
     *   1.0 results, this object will be of type <code>XPathResult</code>.
     * @exception XPathException
     *   TYPE_ERR: Raised if the result cannot be converted to return the 
     *   specified type.
     * @exception DOMException
     *   WRONG_DOCUMENT_ERR: The Node is from a document that is not supported 
     *   by the XPathEvaluator that created this 
     *   <code>XPathExpression</code>.
     *   <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
     *   context node.   
     * 
     * @see org.w3c.dom.xpath.XPathExpression#evaluate(Node, short, XPathResult)
     * @xsl.usage internal
     */
    public Object evaluate(
        Node contextNode,
        short type,
        Object result)
        throws XPathException, DOMException {
            
        // If the XPathEvaluator was determined by "casting" the document    
        if (m_doc != null) {
        
            // Check that the context node is owned by the same document
            if ((contextNode != m_doc) && (!contextNode.getOwnerDocument().equals(m_doc))) {
                String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_DOCUMENT, null);       
                throw new DOMException(DOMException.WRONG_DOCUMENT_ERR, fmsg);
            }
            
            // Check that the context node is an acceptable node type
            short nodeType = contextNode.getNodeType();
            if ((nodeType != Document.DOCUMENT_NODE) &&
                (nodeType != Document.ELEMENT_NODE) && 
                (nodeType != Document.ATTRIBUTE_NODE) &&
                (nodeType != Document.TEXT_NODE) &&
                (nodeType != Document.CDATA_SECTION_NODE) &&
                (nodeType != Document.COMMENT_NODE) &&
                (nodeType != Document.PROCESSING_INSTRUCTION_NODE) &&
                (nodeType != XPathNamespace.XPATH_NAMESPACE_NODE)) {
                    String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_NODETYPE, null);       
                    throw new DOMException(DOMException.NOT_SUPPORTED_ERR, fmsg);
            }
        }
            
        //     
        // If the type is not a supported type, throw an exception and be
        // done with it!
        if (!XPathResultImpl.isValidType(type)) {
            String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_INVALID_XPATH_TYPE, new Object[] {new Integer(type)});       
            throw new XPathException(XPathException.TYPE_ERR,fmsg); // Invalid XPath type argument: {0}               
        }
        
        // Create an XPathContext that doesn't support pushing and popping of
        // variable resolution scopes.  Sufficient for simple XPath 1.0
        // expressions.
        //    Cache xpath context?
        XPathContext xpathSupport = new XPathContext(false);
        
        // if m_document is not null, build the DTM from the document 
        if (null != m_doc) {
            xpathSupport.getDTMHandleFromNode(m_doc);
        }

        XObject xobj = null;
        try {
            xobj = m_xpath.execute(xpathSupport, contextNode, null);         
        } catch (TransformerException te) {
            // What should we do here?
            throw new XPathException(XPathException.INVALID_EXPRESSION_ERR,te.getMessageAndLocation()); 
        }

        // Create a new XPathResult object
        // Reuse result object passed in?
        // The constructor will check the compatibility of type and xobj and
        // throw an exception if they are not compatible.
        return new XPathResultImpl(type,xobj,contextNode, m_xpath);
    }

}